["The Environmental Protection Agency proposed to force tractors, bulldozers and other diesel vehicles that do not run on roads to cut their harmful exhausts by 90% or more. The new regulations, if imposed after public comment, would have a dramatic impact on air quality, particularly in such pollution-choked regions as Los Angeles and California's San Joaquin Valley. Although relatively few in number, these vehicles, which are only modestly regulated, account for 44% of the particulate matter, or soot, and 12% of the smog-producing nitrogen oxides from all vehicles nationwide." Los Angeles Times (April 16, 2003) A26.]
Diesel emission program summary. 1 p.
http://www.epa.gov/nonroad/f03008.htm
Notice of Proposed Rulemaking. 440 p.
http://www.epa.gov/nonroad/preamb0415.pdf
Revised Rules. 181 p.
http://www.epa.gov/nonroad/reg041503.pdf